Metal matrix composite granules and methods of making and using the same

ABSTRACT

Metal matrix composite granules are disclosed comprising a ceramic phase dispersed in a matrix phase. The matrix phase includes aluminum or an aluminum alloy. The granules have an average particle size in the range of from about 100 μm to about 1,000 μm. Also disclosed are methods for producing the granules or articles or processes for using the granules to produce various articles, among other things.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/127,444, filed on Mar. 3, 2015. That application is herebyfully incorporated by reference herein.

BACKGROUND

The present disclosure relates to metal matrix composite granulesincluding a ceramic phase dispersed in a matrix phase. The matrix phaseincludes aluminum or an aluminum alloy. The granules are a metalcomposite powder having an average particle size in the range of fromabout 100 μm to about 1,000 μm. The disclosure also relates to methodsfor producing the granules and methods for using the compositions toproduce articles, among other things.

Metal matrix composites are composite materials including a metal matrixand a reinforcing material (e.g., a ceramic material or an organiccompound) dispersed in the metal matrix. The metal matrix phase istypically continuous whereas the reinforcing dispersed phase istypically discontinuous. The reinforcing material may serve a structuralfunction and/or change one or more properties of the material. Metalmatrix composites can provide combinations of mechanical and physicalproperties that cannot be achieved through conventional materials orprocess techniques. These property combinations have made metal matrixcomposites particularly useful in transport industries where weight,strength, and stiffness are important (e.g., the aerospace andautomotive industries).

Powder metallurgy is a process by which powdered materials are compactedinto a desired shape and sintered to produce desired articles. Powdermetallurgy allows for a faster quenching rate of the metal from the meltwhich typically results in smaller grain sized, increased solidsolubility of most solute elements, and reduced segregation ofintermetallic phases. These results may lead to beneficial properties inthe produced articles, such as high strength at normal and elevatedtemperatures, high modulus values, good fracture toughness, low fatiguecrack growth rate, and high resistance to stress corrosion cracking.

Known compositions and methods for producing articles containing metalmatrix composites have several deficiencies. Achieving a desireddistribution of the reinforcing material throughout the metal matrix canbe difficult. Long and expensive degassing procedures may be required.Handling hazards and difficulties such as explosions, clogging, andrat-holing may also occur. A large number of process steps may berequired to make parts and this may also result in higher yield lossesat each process stage. Compaction of granules provides a direct, simpleand cost-effective route to make parts (herein referred to as directpowder processing). Compaction may lead to articles that are not fullydense and have lower properties. An unacceptable level of oxides mayform in powder metallurgy processes, reducing the properties of themanufactured articles.

It would be desirable to provide compositions and methods for producingarticles containing metal matrix composites via powder metallurgy thatovercome the aforementioned deficiencies allowing for efficient, safe,and cost-effective manufacturing.

BRIEF DESCRIPTION

The present disclosure relates to compositions that include metal matrixcomposite granules, the granules including a ceramic phase dispersed ina matrix phase. The matrix phase includes aluminum or an aluminum alloy.The metal matrix composite granules have an average particle size in therange of from about 100 μm to about 1,000 μm. The disclosure alsorelates to methods for producing the granules and methods for using thecompositions.

Disclosed in various embodiments are compositions including granules ofa metal matrix composite. The metal matrix composite includes a ceramicdispersed phase in an aluminum or aluminum alloy matrix. The granuleshave an average particle size of from about 100 μm to about 1,000 μm.

In some embodiments, the granules have an average particle size of fromabout 200 μm to about 800 μm.

The ceramic dispersed phase may include at least one ceramic materialselected from the group consisting of carbides, oxides, silicides,borides, and nitrides.

In some embodiments, the ceramic dispersed phase comprises at least oneceramic material selected from the group consisting of silicon carbide,titanium carbide, boron carbide, silicon nitride, titanium nitride,zirconium oxide, aluminum oxide, aluminum nitride, and titanium oxide.

The aluminum alloy may include at least one element selected from thegroup consisting of chromium, copper, lithium, magnesium, manganese,nickel, iron, vanadium, zinc, and silicon.

In some embodiments, the aluminum alloy includes from about 91.2 wt % toabout 94.7 wt % aluminum, from about 3.8 wt % to about 4.9 wt % copper,from about 1.2 wt % to about 1.8 wt % magnesium, and from about 0.3 wt %to about 0.9 wt % manganese.

The aluminum alloy may include from about 95.8 wt % to about 98.6 wt %aluminum, from about 0.8 wt % to about 1.2 wt % magnesium, and fromabout 0.4 wt % to about 0.8 wt % silicon. In additional embodiments,these aluminum alloys can also include from about 0.15 wt % to about 0.4wt % copper, and 0.04 wt % to about 0.35 wt % chromium.

In some embodiments, the granules comprise from about 1 vol % to about45 vol % of the ceramic dispersed phase, including from about 1 vol % toabout 35 vol % and from about 15 vol % to about 30 vol %.

Disclosed in other embodiments are methods for producing granules of ametal matrix composite. The methods include high energy mixing metalparticles and ceramic particles to form the granules. The granulesinclude a dispersed phase formed from the ceramic particles and a matrixphase formed from the metal particles. The granules have an averageparticle size of from about 100 μm to about 1,000 μm. The metalparticles comprise aluminum or an aluminum alloy, which are reinforcedin the granules with the ceramic particles.

The granules may have an average particle size of from about 200 μm toabout 800 μm.

In some embodiments, the ceramic particles include at least one ceramicmaterial selected from the group consisting of carbides, oxides,silicides, borides, and nitrides.

The ceramic particles may include at least one ceramic material selectedfrom the group consisting of silicon carbide, titanium carbide, boroncarbide, silicon nitride, titanium nitride, zirconium oxide, aluminumoxide, aluminum nitride, and titanium oxide.

In some embodiments, the ceramic particles have an average particle sizein the range of from about 0.2 μm to about 10 μm, including from about1.5 μm to about 3.5 μm. The size of the ceramic reinforcement particlescan be selected depending on the strength and mechanical propertiesrequired.

The ceramic particles may have an average particle size in the range offrom about 1 μm to about 4 μm, including from about 2 μm to about 3 μm.Alternatively, the ceramic particles may have an average particle sizein the range of from about 0.2 μm to about 0.4 μm or from about 0.5 μmto about 0.9 μm.

In some embodiments, the metal particles, prior to manufacture of thegranules, have an average particle size in the range of from about 5 μmto about 150 μm.

The metal particles may have an average particle size in the range offrom about 15 μm to about 75 μm.

In some embodiments, the metal particles have an average particle sizein the range of from about 20 μm to about 30 μm.

The granules may include from about 1 vol % to about 45 vol % of thedispersed phase.

Disclosed in further embodiments are methods for producing an article.The methods include densifying a preform. The preform includes granulesof a metal matrix composite. The metal matrix composite includes aceramic dispersed phase in an aluminum or aluminum alloy matrix. Thegranules have an average particle size of from about 100 μm to about1,000 μm. Also disclosed are the various articles produced by theseprocesses.

In some embodiments, the granules comprise from about 1 vol % to about45 vol % of the dispersed phase.

These and other non-limiting characteristics of the disclosure are moreparticularly disclosed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings, which arepresented for the purposes of illustrating the exemplary embodimentsdisclosed herein and not for the purposes of limiting the same.

FIG. 1 is a flow chart illustrating an exemplary method for formingmetal matrix composite granules in accordance with some embodiments ofthe present disclosure.

FIG. 2 is an optical image of the microstructure of exemplary granulesof the present disclosure.

FIG. 3 is a flow chart illustrating an exemplary method for forming anarticle using metal matrix composite granules in accordance with someembodiments of the present disclosure.

FIG. 4 is an exploded, cross-sectional view of an apparatus that can beused to perform some exemplary methods of the present disclosure.

FIG. 5 is a photograph illustrating a side-by-side comparison of a coldcompact preform and a hot forged preform (at 125 tons) of the presentdisclosure.

FIG. 6 is a photograph illustrating a side-by-side comparison of a coldcompact preform and a hot forged article (at 150 tons) of the presentdisclosure.

FIG. 7 is a photograph illustrating a side-by-side comparison of a coldcompact preform and a hot forged article (at 200 tons) of the presentdisclosure.

FIG. 8 is an optical image of the microstructure of a hot forged article(at 125 tons) of the present disclosure.

FIGS. 9A and 9B are photographs of discs that have been open die forgedaccording to embodiments of the present disclosure.

FIG. 10 is another flowchart showing process steps in accordance withthe methods of the present disclosure

FIG. 11 is a set of pictures showing various intermediate products whenusing hot forging methods.

FIG. 12 is a set of pictures showing various intermediate products whenusing hot extrusion methods.

DETAILED DESCRIPTION

A more complete understanding of the components, processes andapparatuses disclosed herein can be obtained by reference to theaccompanying drawings. These figures are merely schematicrepresentations based on convenience and the ease of demonstrating thepresent disclosure, and are, therefore, not intended to indicaterelative size and dimensions of the devices or components thereof and/orto define or limit the scope of the exemplary embodiments.

Although specific terms are used in the following description for thesake of clarity, these terms are intended to refer only to theparticular structure of the embodiments selected for illustration in thedrawings, and are not intended to define or limit the scope of thedisclosure. In the drawings and the following description below, it isto be understood that like numeric designations refer to components oflike function.

The singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise.

As used in the specification and in the claims, the term “comprising”may include the embodiments “consisting of” and “consisting essentiallyof.” The terms “comprise(s),” “include(s),” “having,” “has,” “can,”“contain(s),” and variants thereof, as used herein, are intended to beopen-ended transitional phrases, terms, or words that require thepresence of the named components/steps and permit the presence of othercomponents/steps. However, such description should be construed as alsodescribing compositions or processes as “consisting of” and “consistingessentially of” the enumerated components/steps, which allows thepresence of only the named components/steps, along with any impuritiesthat might result therefrom, and excludes other components/steps.

Numerical values in the specification and claims of this applicationshould be understood to include numerical values which are the same whenreduced to the same number of significant figures and numerical valueswhich differ from the stated value by less than the experimental errorof conventional measurement technique of the type described in thepresent application to determine the value.

All ranges disclosed herein are inclusive of the recited endpoint andindependently combinable (for example, the range of “from 2 to 10” isinclusive of the endpoints, 2 and 10, and all the intermediate values).

The term “about” can be used to include any numerical value that canvary without changing the basic function of that value. When used with arange, “about” also discloses the range defined by the absolute valuesof the two endpoints, e.g. “about 2 to about 4” also discloses the range“from 2 to 4.” The term “about” may refer to plus or minus 10% of theindicated number.

The present disclosure refers to granules having an average particlesize. The average particle size for granules is defined as the particlediameter at which a cumulative percentage of 50% by weight of thegranules are attained. In other words, 50 wt % of the granules have adiameter above the average particle size, and 50 wt % of the granuleshave a diameter below the average particle size.

The present disclosure also refers to particles as having an averageparticle size. The average particle size for particles is defined as theparticle diameter at which a cumulative percentage of 50% by volume ofthe particles are attained. In other words, 50 vol % of the particleshave a diameter above the average particle size, and 50 vol % of theparticles have a diameter below the average particle size.

The present disclosure relates to metal matrix composite granulesincluding a ceramic phase dispersed in a matrix phase. The matrix phaseincludes aluminum or an aluminum alloy. The granules have an averageparticle size in the range of from about 100 μm to about 1,000 μm. Thedisclosure also relates to methods for producing the granules andmethods for using compositions containing such granules.

The compositions of the present disclosure allow metal compositecomponents to be made using cost-effective, high-yield direct powderprocesses. This minimizes the number of process steps from raw materialto the final article shape. The distribution of the ceramic particles isachieved at the granule stage which is important for product qualityassurance.

The granules of the present disclosure have lower surface area to volumeratios compared to powders. The increased granule size reduces thepotential for surface oxidation and makes compaction easier. Fully-densecompacts can be produced with lower deformation (e.g., sheardeformation) and at reduced temperatures and/or pressures.

The relatively large granule size also provides additional processingand handling benefits. For example, explosion hazards are reduced in theindustrial environment; and enhanced aid flow characteristics can beachieve to avoid clogging and rat-holing in feeder equipment. Theparticle size of the granules may be controlled using sieves.

The methods of the present disclosure may be performed in a dry, inertatmosphere. Processing in such an atmosphere produces an effectivedegassing procedure and reduces the need for long and expensivedegassing procedures later on. Direct powder processing also reduces thenumber of process steps required to make parts and allows for higheryield. In direct powder processing, powder is compacted and shapeddirectly into the desired part, instead of being remelted into a moltenform and then shaped into the desired part. Warm degass procedures canbe applied after initial powder compaction to remove any moisture frompowder surfaces.

FIG. 1 is a flowchart showing a general method 100 for forming metalmatrix composite granules of the present disclosure. The method includesproviding metal particles 105 and providing ceramic particles 110 to ahigh energy mixing stage 120. In the mixing stage 120, metal matrixcomposite granules are formed. The granules are then sorted 130 toprovide a composition of granules having an average size in the range offrom about 100 μm to about 1,000 μm. The granules may have an averageparticle size in the range of from about 200 μm to about 800 μm,including from about 300 to about 700 μm and from about 400 to about 600μm.

The high energy mixing 120 may be performed using one or more of ballmilling, teemer mills, attritors, rotary mills, and granulators.

The metal particles 105 include aluminum or an aluminum alloy. Thealuminum alloy may include at least one element selected from chromium,copper, lithium, magnesium, nickel, and silicon. It is noted that“aluminum,” as used here, refers to aluminum with only impuritiespresent, i.e. pure aluminum, whereas the term “aluminum alloy” is usedto refer to alloys of aluminum with a significant amount of anotherelement.

In some embodiments, the aluminum alloy is a 1000 series alloy 99 wt %aluminum), a 2000 series alloy (including copper as an alloyingcomponent), a 3000 series alloy (including manganese as an alloyingcomponent), a 4000 series alloy (including silicon as an alloyingcomponent), a 5000 series alloy (including magnesium as an alloyingcomponent), a 6000 series alloy (including magnesium and silicon asalloying components), a 7000 series alloy (including zinc as an alloyingcomponent), or an 8000 series alloy (e.g., aluminum-lithium alloys).

The metal particles may have an average particle size in the range offrom about 5 μm to about 150 μm, including from about 15 μm to about 75μm, about 20 μm to about 50 μm, from about 20 μm to about 40 μm, fromabout 20 μm to about 30 μm, and about 75 μm.

In some embodiments, the aluminum alloy includes from about 91.2 wt % toabout 94.7 wt % aluminum, from about 3.8 wt % to about 4.9 wt % copper,from about 1.2 wt % to about 1.8 wt % magnesium, and from about 0.3 wt %to about 0.9 wt % manganese.

In other embodiments, the aluminum alloy includes from about 95.8 wt %to about 98.6 wt % aluminum, from about 0.8 wt % to about 1.2 wt %magnesium, and from about 0.4 wt % to about 0.8 wt % silicon. Inadditional embodiments, these aluminum alloys can also include fromabout 0.15 wt % to about 0.4 wt % copper, and 0.04 wt % to about 0.35 wt% chromium.

The aluminum alloy may be 2009. The composition of 2009 aluminum alloyis as follows:

2009 Component Wt % Aluminum Remainder Copper 3.2-4.4 Iron Max 0.2 Magnesium 1.0-1.6 Oxygen Max 0.6  Silicon Max 0.25 Zinc Max 0.25

The aluminum alloy may be 2124. The composition of 2124 aluminum alloyis as follows:

2124 Component Wt % Aluminum 91.2-94.7 Chromium Max 0.1  Copper 3.8-4.9Iron Max 0.3  Magnesium 1.2-1.8 Manganese 0.3-0.9 Other, each Max 0.05Other, total Max 0.15 Silicon Max 0.2  Titanium Max 0.15 Zinc Max 0.25

The aluminum alloy may be 2618. The composition of 2618 aluminum alloyis as follows:

2618 Component Wt % Aluminum Balance Copper 1.9-2.7 Iron 0.9-1.3Magnesium 1.3-1.8 Nickel 0.9-1.2 Silicon Max 0.25 Titanium 0.04-0.1 Others, each Max 0.05 Others, total Max 0.15

The aluminum alloy may be 6061. The composition of 6061 aluminum alloyis as follows:

6061 Component Wt % Aluminum 95.8-98.6 Chromium 0.04-0.35 Copper0.15-0.4  Iron Max 0.7  Magnesium 0.8-1.2 Manganese Max 0.15 Other, eachMax 0.05 Other, total Max 0.15 Silicon 0.4-0.8 Titanium Max 0.15 ZincMax 0.25

The aluminum alloy may be 6082. The composition of 6082 aluminum alloyis as follows:

6082 Component Wt % Aluminum 95.2-98.3 Chromium  Max 0.25 Copper Max 0.1Iron Max 0.5 Magnesium 0.6-1.2 Manganese 0.4-1.0 Other, total  Max 0.15Silicon 0.7-1.3 Titanium Max 0.1 Zinc Max 0.2

The ceramic particles 110 include at least one material selected fromcarbides, oxides, silicides, borides, and nitrides. In some embodiments,the material is selected from silicon carbide, titanium carbide, boroncarbide, silicon nitride, titanium nitride, zirconium oxide, aluminumoxide, aluminum nitride, and titanium oxide.

The ceramic particles may have an average particle size in the range offrom about 0.1 μm to about 20 μm, including from about 0.2 μm to about10 μm, and from about 1 μm to about 4 μm. In other embodiments, theceramic particles have an average particle size in the range of fromabout 0.2 μm to about 0.4 μm, or from about 0.5 μm to about 0.9 μm.

The granules produced by the high energy mixing 120 may contain up toabout 45 vol % of a ceramic phase dispersed in a metal matrix phase. Insome embodiments, the granules include from about 1 vol % to about 35vol % of the ceramic dispersed phase, including from about 5 to about 30vol %, from about 10 to about 25 vol %, and about 20 vol %.

FIG. 2 is an optical image of a plurality of granules.

If necessary, the granules may be sorted 130 to obtain a compositionhaving the desired grain size.

FIG. 3 is a flow chart illustrating an exemplary method 300 for formingan article using the granules. The method includes providing thegranules 330; compacting the granules to make a preform 340; and thenhot forging or hot extruding the preform 350.

During compacting 340, the granules are cold compacted into a desiredshape to make a preform. The cold compacting coalesces the particles andincreases density. However, the preform is not close to fully dense. Inparticular embodiments, the cold compacting is performed using a tooldiameter of about 50 mm to about 70 mm, with a load of about 80 tons toabout 90 tons. In other embodiments, the cold compacting is performedusing a tool diameter of about 50 mm to about 70 mm, with an exertedpressure of about 250 MPa to about 330 MPa. Of course, the tooldiameter, exerted pressure, and load can be larger as well, as mightoccur in commercial production processes. The cold compacting can alsobe done by cold isostatic pressing, in which the granules are exposed toa high gas pressure in a high pressure containment vessel, to turn thegranules into a compact solid, i.e. a billet. In either case, warmdegass procedures can be applied after initial powder compaction toremove any moisture from powder surfaces.

Next, the preform is hot forged or hot extruded 350. The hot forging maybe performed at a temperature in the range of from about 300° C. toabout 600° C., including from about 400° C. to about 500° C., and about450° C.

FIG. 4 illustrates an exemplary apparatus 360 that may be used tocompact the granules into the preform 365. The apparatus 360 includes apunch 361, a pot die 362, and an ejector 363. A slug 364 may be placedupon the preform 365 during compacting 340. The slug 364 may be etchedoff after compacting/extruding. In some embodiments, the slug 364 is acopper can.

The articles (e.g., billets) formed from these methods may be used asinputs for further processing to form final articles.

FIG. 10 illustrates an exemplary method 700 in accordance withembodiments of the present disclosure. The method 700 includes providingraw materials (e.g., aluminum powder and silicon carbide particles 780);high energy mixing the raw materials to form granules 781; coldcompacting 782 (e.g., via die compaction or cold isostatic pressing);hot compacting 783 (e.g., via forging or extruding); and finish forgingor extruding 784.

FIG. 11 shows some pictures of the intermediate products at each stepwhen hot forging 883 is used. A micrograph of the granules is labeled885. The die compaction unit is labeled 886. The cold die compactedgranules are labeled 887, while the granules after hot forging arelabeled 888. The final forged disc is labeled 889.

FIG. 12 shows some pictures of the intermediate products at each stepwhen hot extruding 983 is used. A picture of the granules is labeled990. A billet obtained after cold isostatic pressing is labeled 991. Thebillet is then hot extruded at 60 mm diameter, and a picture of theresulting bar is labeled 992. The bar is then die forged into a disc,which is labeled 993.

Non-limiting examples of final articles that the compositions, systems,and methods of the present disclosure can be used to produce includediscs, pistons, con rods, and piston pins.

The following examples are provided to illustrate the compositions,articles, and methods of the present disclosure. The examples are merelyillustrative and are not intended to limit the disclosure to thematerials, conditions, or process parameters set forth therein.

EXAMPLES Example 1 Cold Compaction

Granules having the composition of AMC225XE (commercially available fromMaterion Corporation) were cold compacted using various tool diameters(from about 15 to about 60 mm) and loads (from about 30 to about 100tons). AMC225XE includes silicon carbide particles dispersed in a matrixof aluminum alloy 2124. The results are provided in the table below.

Tool diameter Load Pressure Average (mm) (tons) Exerted (MPa) Density %Comment 15 30 1665 ~97 30 50 694 ~80 60 50 173 — Too crumbly to takemeasurements 60 70 243 — Too crumbly 60 80 277 ~71 Powder held shapewell, came out easily 60 90 312 ~76 Powder held shape well, came outeasily 60 100 347 ~76 Sample stuck in tool

Hot Forging

Next, a 60 mm diameter die was used to compact the samples from the 90ton load. The preforms were hot forged at a temperature of 450° C.Experiments were performed with and without lubrication. However, thecompacted samples from the unlubricated experiments could not beextracted.

Loads of 125 tons, 150 tons, and 200 tons were tested. The results areprovided in the table below and in FIGS. 5-8.

Load (tons) Pressure Exerted (MPa) Average Density % 125 434 99.7 150520 99.8 200 694 99.9

FIG. 5 shows the cold preformed material 470 and hot forged article 475of the 125 ton load test. FIG. 6 shows the cold preformed material 570and hot forged article 575 of the 150 ton load test. FIG. 7 shows thecold preformed material 670 and hot forged article 675 of the 200 tontest. FIG. 8 is an optical image of the surface of the hot forgedarticle 475 of FIG. 5.

Die Forging

The articles were subsequently die forged. FIG. 9A is a photograph ofsix pucks die forged from the 125 ton load test. FIG. 9B is a photographof two pucks die forged from the 150 ton load test and one puck dieforged from the 200 ton load test.

The present disclosure has been described with reference to exemplaryembodiments. Obviously, modifications and alterations will occur toothers upon reading and understanding the preceding detaileddescription. It is intended that the present disclosure be construed asincluding all such modifications and alterations insofar as they comewithin the scope of the appended claims or the equivalents thereof.

1. A composition comprising granules of a metal matrix composite;wherein the metal matrix composite comprises a ceramic dispersed phasein an aluminum or aluminum alloy matrix; and wherein the granules havean average particle size of from about 100 μm to about 1,000 μm.
 2. Thecomposition of claim 1, wherein the granules have an average particlesize of from about 200 μm to about 800 μm.
 3. The composition of claim1, wherein the ceramic dispersed phase comprises at least one ceramicmaterial selected from the group consisting of carbides, oxides,silicides, borides, and nitrides.
 4. The composition of claim 1, whereinthe ceramic dispersed phase comprises at least one ceramic materialselected from the group consisting of silicon carbide, titanium carbide,boron carbide, silicon nitride, titanium nitride, zirconium oxide,aluminum oxide, aluminum nitride, and titanium oxide.
 5. The compositionof claim 1, wherein the aluminum alloy further comprises at least oneelement selected from the group consisting of chromium, copper, lithium,magnesium, manganese, nickel, iron, vanadium, zinc, and silicon.
 6. Thecomposition of claim 1, wherein the aluminum alloy comprises from about91.2 wt % to about 94.7 wt % aluminum, from about 3.8 wt % to about 4.9wt % copper, from about 1.2 wt % to about 1.8 wt % magnesium, and fromabout 0.3 wt % to about 0.9 wt % manganese.
 7. The composition of claim1, wherein the aluminum alloy comprises from about 95.8 wt % to about98.6 wt % aluminum, from about 0.8 wt % to about 1.2 wt % magnesium, andfrom about 0.4 wt % to about 0.8 wt % silicon.
 8. The composition ofclaim 1, wherein the granules comprise from about 1 vol % to about 45vol % of the ceramic dispersed phase.
 9. A method for producing granulesof a metal matrix composite, the method comprising: high energy mixingmetal particles and ceramic particles to form the granules; wherein thegranules comprise a dispersed phase formed from the ceramic particlesand a matrix phase formed from the metal particles; wherein the granuleshave an average particle size of from about 100 μm to about 1,000 μm;and wherein the metal particles comprise aluminum or an aluminum alloy.10. The method of claim 9, wherein the granules have an average particlesize of from about 200 μm to about 800 μm.
 11. The method of claim 9,wherein the ceramic particles comprise at least one ceramic materialselected from the group consisting of carbides, oxides, silicides,borides, and nitrides.
 12. The method of claim 9, wherein the ceramicparticles comprises at least one ceramic material selected from thegroup consisting of silicon carbide, titanium carbide, boron carbide,silicon nitride, titanium nitride, zirconium oxide, aluminum oxide,aluminum nitride, and titanium oxide.
 13. The method of claim 9, whereinthe ceramic particles have an average particle size in the range of fromabout 0.2 μm to about 10 μm.
 14. The method of claim 9, wherein theceramic particles have an average particle size in the range of fromabout 1 μm to about 4 μm.
 15. The method of claim 9, wherein the metalparticles have an average particle size in the range of from about 5 μmto about 150 μm.
 16. The method of claim 9, wherein the metal particleshave an average particle size in the range of from about 15 μm to about75 μm.
 17. The method of claim 9, wherein the granules comprise fromabout 1 vol % to about 45 vol % of the dispersed phase.
 18. A method forproducing an article comprising: densifying a preform; wherein thepreform comprises granules of a metal matrix composite; wherein themetal matrix composite comprises a ceramic dispersed phase in analuminum or aluminum alloy matrix; and wherein the granules have anaverage particle size of from about 100 μm to about 1,000 μm.
 19. Themethod of claim 18, wherein the granules comprise from about 1 vol % toabout 45 vol % of the dispersed phase.
 20. An article formed fromgranules of a metal matrix composite, the metal matrix compositioncomprising a ceramic dispersed phase in an aluminum or aluminum alloymatrix, and the granules having an average particle size of from about100 μm to about 1,000 μm.